Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper or lightly grease it.
Roll out the dough on a lightly floured surface into a 9×13-inch rectangle. If using crescent dough, press seams together to form a solid sheet.
Add the filling: Sprinkle mozzarella, pepperoni, Parmesan, garlic powder, and Italian seasoning evenly across the dough.
Roll it up tightly from the long edge. Pinch the seam and ends to seal. Place seam-side down.
Slice into 12 pieces using a serrated knife or unflavored dental floss.
Arrange rolls cut-side up on the prepared baking sheet.
Brush tops with butter mixed with garlic powder. Sprinkle Parmesan and parsley if using.
Bake for 15–18 minutes, or until golden brown and bubbling.
Cool slightly and serve warm with marinara sauce on the side.